Gulf of Maine Warming Update: 2022 the Regions Second Warmest Year
Documenting one more year in a decade of above-average regional temperatures
With an annual average sea surface temperature (SST) of 53.66°F — more than 3.72°F above normal — the Gulf of Maine experienced its 2nd warmest year on record in 2022. The region ranked in the top 3 warmest temperatures across all seasons, with the most extreme temperatures occurring in November.
Annual Sea Surface Temperatures
The annual average SST in the Gulf of Maine for 2022 was 53.66°F; this was 3.72°F above the long-term (i.e., 1982-2011) average. This year fell short of the previous warmest year on record — 2021 — 0.43°F. Since the early 1980s, the rate of warming in the Gulf of Maine 0.86°F / Decade has been more than triple that of the world’s oceans (0.27°F / Decade Figure 1).
r report_yr, illustrating that r report_yr was the 2nd warmest year on record. Long-term trendlines for the Gulf of Maine (blue) and the entire globe (green) show how much more quickly the Gulf of Maine is warming compared to the rest of the world.The rate of warming in the region vary throughout the year. Comparisons across the four seasons (Figure 2) reveal that the Gulf of Maine is warming fastest during the July-September (nearly 4x the global ocean average), more than twice the rate seen during January-March (~3x the global ocean average).
There can be significant spatial variability in annually-averaged SST patterns. The Gulf of Maine in 2022 illustrated this fact with the region southeast of Georges Bank experiencing the highest SST anomalies (Figure 3). This area is more susceptible than other areas of the Gulf of Maine to large-scale variability in major oceanic currents, such as the relative influence of the Gulf Stream versus the Labrador Current.
Looking at these spatial patterns in 3-month averages (Figure 4) shows just how “patchy” these pockets of above-average temperatures can be. During January-March, the areas to the south and southeast of the Gulf of Maine exhibit a strong mix of both above and below average surface temperature. During April-June, we can see that the water within the Gulf of Maine itself and the deeper waters just south of Georges Bank experienced warmer temperatures than the surrounding areas. In the second-half of the year, the exceptional warmth of the Gulf Stream is evident to the east and south of the area of study (dashed line), while the Gulf of Maine, itself, remains several degrees above the long-term average.
When we compare the annual average SST for 2022 (53.66°F) to other unusually warm years in the Gulf of Maine, we see that it was ~0.4°F cooler than 2021, the warmest year on record(54.09°F). When we look at the deviation from the long-term average SST (i.e., the annual SST anomaly), the last decade stands out for its exceptional warmth (Figure 5). 2022 continues a pattern that began in 2010 of sustained above-average temperatures. With the exception of 2019 (ranked 13th), all of the last ten years remain in the top 10 for SST.
Worldwide Temperatures
It was not just the Gulf of Maine that experienced exceptional warmth in 2022, however. Globally, 2022 was the 3rd warmest year for sea surface temperatures, and 6th-warmest for combined land & ocean temperatures..
Figure 6 shows annual average SST anomalies for oceans all over the world in 2022. While much of the Southern Ocean and expanses of the southeastern Pacific were anomalously cool (a feature of La Niña conditions), most of the world’s oceans experienced unusually warm temperatures in 2022. This is particularly true for northern mid-latitudes, especially the northwestern Pacific (off Japan) and along the eastern seaboard of the United States—a region that includes the Gulf of Maine.
Daily Sea Surface Temperatures
The annual cycle of SST in the Gulf of Maine exhibits a familiar pattern with the lowest annual temperatures being observed in March, while the highest SSTs are observed in August (Figure 7). The average difference between the annual maximum SST in August and the annual minimum SST in March is 22.87 °F. In 2022, the difference between the maximum SST (Aug-07, 68.72°F) and minimum SST (Mar-19, 42.15°F) was 26.57 °F. Daily SST anomaly values never fell below +1.59 °F and reached as high as +7.36 °F above the long-term average.
Record Setting Daily Temperatures
?@fig-hottest-days shows the highest SST values ever recorded for each day of the year in the Gulf of Maine. Record-setting days that occurred in 2022 are denoted with dark red dots (?@fig-hottest-days). Indeed, daily high SST records were set for more than half of all days in November and December. The most daily records were set in November, which experienced record high SSTs for 24 of the month’s 30 days - or 80% of the month. In total, record high daily temperatures were reached on 169 days during2022; nearly 46% of days in 2022 experienced record high SSTs in the Gulf of Maine.
More Persistent, Intense Heatwaves
A marine heatwave (MHW) is defined as a period when there are five or more consecutive days when the observed SST is greater than the 90th percentile of the long-term average for that day. Subsequent MHW periods that are separated by two or fewer daily average SSTs that fall below the threshold are still considered part of a MHW event. Figure 7 shows the long-term average SST (gray line labeled “Climatological Mean”), as well as the threshold for a MHW day (gray line labeled “Heatwave Threshold”). The solid line and shaded area in the figure shows the observed SST for that day and its distance from the climatological average; when it is red, the Gulf of Maine is experiencing MHW conditions.
The Gulf of Maine met the criteria for MHW status for 353 days in 2022. While the warmest temperatures of the year were experienced in August (as we would expect from the climatology for the region), the largest temperature anomalies were observed during the last days of November, when they breached 7 °F above the long-term average.
Comparing daily SST anomalies and MHW status for 2022 to the long-term record (Figure 9), as in the figure below — it becomes clear that the frequency, duration, and intensity of MHWs has not only increased in the past decade. In a world without human-caused climate change, we would expect, positive (warm) and negative (cool) SST anomalies to more or less balance out over the span of several years, as various patterns of natural climate variability alternate having a dominant influence in Earth’s climate (e.g., La Niña vs El Niño). What is being observed in the Gulf of Maine (and elsewhere around the world), however, is a loss of that balance: larger fractions of recent years are experiencing above average temperatures and cold spells are becoming vanishingly rare.
Warming Rate
GMRI research was the first to reveal that the Gulf of Maine has been warming faster than the vast majority of the world’s ocean. Figure 10 updates this historical analysis by including data for 2022. Indeed, the story has not changed: the Gulf of Maine is warming faster than ~96.6% of the world’s ocean. The reason why this is so important is because the rate of change can have profound consequences for the biology of individual species and for the integrated ecology of entire food webs.
Concluding Thoughts:
In recent years, SSTs in the Gulf of Maine (and adjacent waters) have increased significantly and the rate of warming has accelerated. Combined, these climate-related impacts are beginning to have profound consequences for the marine ecology in the Gulf of Maine, with implications for the people and communities who rely on marine resources for their livelihoods and well-being. Research suggests there are two major factors driving these trends, one oceanographic and one atmospheric:
Oceanographic: The Gulf of Maine is influenced by two primary oceanic currents: the Labrador Current and the Gulf Stream. Historically, there was a stronger influence of the Labrador Current on the water in the Gulf of Maine. That stronger flow helped keep the heat transported northward along the U.S. East Coast by the Gulf Stream further out to sea. More recently, scientists have observed changes occurring in the interplay between the Labrador Current and Gulf Stream. More Arctic-origin freshwater from melting sea ice and land-based ice is constricting the southward flow of the Labrador Current. This is allowing the Gulf Stream—which transports warm water from lower latitudes to spread out more at latitudes around the Gulf of Maine. This, in turn, allows warmer water, more heavily influenced by the Gulf Stream to “spill over” into the Gulf of Maine.
Atmospheric: The North Atlantic Oscillation (NAO)— a large-scale pattern of natural variability in the atmosphere — has been in a “positive phase” more frequently over the past 10-15 years, meaning a more zonal (i.e., west-to-east) atmospheric pattern has dominated in the region. The relative decrease in “waviness” of the jet stream inhibits more consistent intrusions of cooler, Arctic air into the region.
While the oceanographic driver of the observed SST change in the Gulf of Maine has clear links to human-caused climate change, more research is needed to ascertain whether the NAO is experiencing significant changes as a result of anthropogenic climate change. Regardless, the atmospheric and oceanic conditions of the past several years combine to reveal an unambiguous trend: The Gulf of Maine is experiencing unprecedented warmth—and is heating up at a rate that is faster than almost anywhere else in the world’s oceans.
A Note on Data Sources
- NOAA High Resolution SST data provided by the NOAA/OAR/ESRL PSL, Boulder, Colorado, USA, from their Web site at https://psl.noaa.gov/data/gridded/data.noaa.oisst.v2.highres.html.
Recommended Citation:
Gulf of Maine Research Institute. 2022. Gulf of Maine Warming Update: 2022 . https://gmri.org/stories/warming-22
OLD ASSETS:
Temperature Anomaly Horizons
One way to think about the severity of these changes is to think about temperature horizons. A temperature horizon captures how long temperatures remain above certain thresholds. Each threshold is designated its own temperature, and in this way we can see how long within a year temperatures remained: 1 to 2 or as much as 4\(^oC\) above normal.
Comparing the Gulf’s Two Hottest Years
If we pull the horizons of our two hottest years on record it makes it easier to contrast where either one experienced acute high temperature events, and where there were sustained periods of above average temperatures.
Early into 2022 it was apparent that the year was on-par with the previous title-holder for warmest year on record.
The Balance of Hot and Cold
Another way to visualize the climate transition that we are observing is by looking at the fraction of each year spent in different temperature ranges. Under a steady climate we would expect over the long-term to spend similar amounts of the year experiencing relatively warm & cold temperatures. These periods would balance themselves out and we would on-average have experienced something similar to the long-term climate.
What we have been seeing in the Gulf of Maine recently has lost that sense of balance. Larger fractions of the year are shared by above average temperatures & cold spell events are becoming vanishingly rare.
